Method for the cooling of gas containing naphthalene



Jan. 11, 1955 s. w. DAHLBECK METHOD FOR THE COOLING OF GAS CONTAINING NAPHTHALENE Filed Oct. 2, 1952 mum/722R. Mal 22V W/L HELM DAHLBECK h/S ATTORNEYS Unitd St21t$ METHODFOR THE COOLING F GAS CONTAINING NAPHTHALENE Sven Wilhelm Dahlbeck, Djursholm, Sweden, assignor, by theme assignments, to Rosenblad. Corporation, New York, N. Y., acorporation of New York Application October 2, 1952, Serial No. 312,841 Claims priority, application Sweden October 6, 1951 3 Claims. (Cl. 183-120) Thepresent invention relates to the cooling of gas containing naphthalene such as, for example, crude gas in the manufacture of town gas,-in the course of which certain difficulties arise in consequence of the naphthalene being precipitated during the cooling of the gas. This can cause interruption of service due to deposits in the actual cooler, as well as in other units connected in series with the cooler for treatment of the cooled gas.

The invention is chiefly applicable to coolers of the shaft or tower type, in which cooling water may be brought to pass, if desired in series, through a number of spraying units, each adapted to spray thecooling water in a very fine form across the cross section of the tower, thus producing a series of showers of cooling water through vi lhich the gas passes in succession while gradually cooling t e gas.

It has been ascertained in the use of such cooling arrangements that, if no special precautionary measures are taken, naphthalene can be precipitated, at least in the cold end of the tower. This can, inter alia, interfere considerably with the working of the spraying units, while the escaping cooled gas may contain naphthalene to an extent that will cause extreme trouble in subsequent processes.

As far as the mere functioning of the cooler proper is concerned, a satisfactory improvement can often be made by adding a naphthalene solvent, e. g. tar with a low naphthalene content, to the cooling water entering the cooler.

Although conditions in the cooler proper can thus be improved, this manner of washing out or extracting the naphthalene present in the form of vapour will be too inadequate to have any marked eifect upon the naphthalene content in the outgoing gas. A suitable tar is hardly ever available in suflicient quantities to provide anything else than a too small drop-contact surface against the gas when mixed with the many times greater quantity of water in the sprays. In addition to this the tar with the water becomes rapidly heated to a temperature unsuitable for cleaning the naphthalene.

The main object of the invention is to efiect the above mentioned dissolution of naphthalene necessary for the proper functioning of the cooler, as well as an effective cleaning of the cooled gas from naphthalene, without necessitating any material increase in the added quantity of naphthalene solvent.

The method according to the invention comprises the steps of supplying an agent for extracting and dissolving naphthalene to a circulating quantity of said agent, spreading said circulating agent, during its circulation, in the shower form across the path of flow of the cooled gas current and supplying the extracting and dissolving agent from the circulating quantity to the cooling water.

By this procedure the solvent can, before it is passed to the cooling section of the cooler and into the cooling water, he brought into contact with the cooled gas under the most favourable conditions for extracting the naphthalene. By keeping the solvent in circulation it can form a shower which, irrespective of the quantity of newly added solvent, contains sufiicient quantities of the latter to establish a large enough drop-contact surface with the gas. It has thus proved advisable to circulate solvent in a quantity of the same order as the quantity of cooling water in the cooling water showers. cooling water, for example, can approximately exceed a This quantity of 8 showers the gas passes and is gradually "ice hundred times the quantity of the solvent, e. .g. receiver tar, which is available in the production of 'town; gas as a suitable solvent in this respect.

The dissolving and extracting medium becomes effec tively cooled in the shower by the previously cooled :gas to practically the same low temperature as the latter, e. g. in cooling crude; gas toabout 15C., at whichtemperature it has a satisfactory extracting capacity. Because of the proportion between circulating and newly added dissolving and extracting agents the temperature of the latter does not acquire any noticeable influence on the temperature of the:shower. This has, inter alia,the advantage that receiver tar, for example, which at the receiver has a temperature of -90" C., can be added to the cooler without pre-cooling.

Examples of some arrangements forthepractical realisation of the invention are illustratedin the accompanying drawing, in which:

Fig. 1 shows a cooling tower, partly in section, with an arrangement for circulating dissolving and extracting medium according tothe invention, and

Fig. 2 shows modification of such a circulating arrangement in the same kind of cooling tower.

In Fig. l a vertical cooling tower 1 of approximately cylindrical cross section is fitted with an inlet 2 and an outlet 3 for gas and a liquid outletla. Arranged centrally in the tower .is a vertical shaft 4, which by means ofa driving belt 5 is driven by a motor 6. A number of spraying units, or sprayers, are placed under one another on shaft 4 in the form of rotating plates. The uppermost of these sprays 7, and the two sprayers 8 and 9 respectively, immediately below, are shown in the sectioned part of the tower. Every such spray has a corresponding collecting channel 11, 12 and 13 respectively, which pass round the inner surface of the tower. Each of these channels is situated at such a level in relation to the respective sprays that it is capable of collecting a liquid ejected in the direction of the mantle surface of the tower from the spray in question.

Cooling water is supplied through valve 14 and pipe 15 to the spray 8. From this it is ejected into the collecting channel 12 in the form of an umbrella-like shower, is drained from there through pipe 16 to the spray 9, ejected from this one in the form of a new shower to the collecting channel 13, and so on, so that there will be a number of showers corresponding to the number of sprays from the spray 8 and underlying sprays. Through these cooled until it leaves the shower from the spray 8 in a finally cooled state.

According to the invention a naphthalene dissolving agent is passed through valve 17 and pipe 18 to the spray 17. From this it is ejected in the form of a shower to the collecting channel 11, covering the flowpath of the cooled gas towards the outlet pipe 3. The collecting channel 11 is drained through pipe 19 to pump 20. The naphthalene solvent can again be circulated by pump 20 via pipe 21 to spray 7. The circulating quantity is controlled by valve 22. Once such a quantity of solvent has been added that its level in the channel 11 has risen to the overflow 23, any further solvent which is added runs over through the overflow and away from the circulating quantity to the collecting channel 12. From here, mixed with the cooling water, it continues to follow the latters course through the cooling tower.

Fig. 2 shows a modification of the arrangement according to Fig. 1, in which the plate-spray 7 and pump 20 are substituted by a type of self-lifting spray 24, well-known in itself. This consists of a conical casing which widens upwards. It emerges with its lower section. into a container 26, which communicates with the collecting channel 11 through the pipe 27. When the spray rotates, the solvent which enters the lower section of the spray from the channel and the container, will be forced up towards the upper edge of the spray, and from there again be ejected in circulation into the channel. In this case a further supply of. solvent is alternatively shown as taking place to the channel direct through valve 28 and pipe 29, but can of course here, as shown in Fig. 1, be carried out 0 at other stages of the path of circulation.

l atented Jan. 11,, 1955 garded as examples by which any person skilled in the art can of course produce innumerable variants within the sphere of this invention.

It should be specially pointed out that although arrangements have only been shown for applying the invention in cooling towers with mainly horizontal showers and a vertical gas flow, it can just as well be used for other directions of showers and gas flows, as e. g. mainly horizontal gas flow and mainly vertical showers.

Nor must the fact, given in the examples, that the shower of circulating solvent is arranged within the cooling tower proper be taken to imply that the invention is restricted to such an embodiment. This shower may also be arranged in a special container etc., which, placed outside the cooling tower, communicates with the outlet of cooled gas from the latter, the outlet for solvents from the circulation circuit being arranged to pass on such solvent at least to some one of the cooling water showers in the tower.

What I claim is:

1. Method of treating hot gas containing naphthalene comprising the steps of cooling the gas by passing it in series through a number of cooling water showers spread across the pathway of the gas, passing the cooled gas in contact with a circulating naphthalene extracting and dissolving liquid while circulating and spreading said circulated extracting and dissolving liquid in the form of a shower across the pathway of the cooled gas, passing from said circulated liquid a portion of said liquid to the cooling Water showers and supplying make up liquid of the same kind to said circulated liquid.

2. A method as claimed in claim 1 wherein the quan- 4 tity of extracting and dissolving liquid circulated per unit of time is maintained at an amount which is a multiple of that of the make up liquid supplied per equal unit of time and which preferably is of the same order as the quantity of cooling water spread per unit of time in each cooling water shower.

3. A method as claimed in claim 2, wherein the make up extracting and dissolving liquid is supplied at a temperature exceeding that of the cooled gas and wherein the extracting and dissolving liquid is circulated in a quantity per unit of time which exceeds the quantity of make up liquid supplied per unit of time to so great an extent that the temperature of the make up liquid will have no material influence on the temperature of the circulated liquid which is cooled by the cooled gas.

References Cited in the file of this patent UNITED STATES PATENTS 679,587 Zellweger July 30, 1901 1,732,086 Flippen Oct. 15, 1929 1,760,335 Becker May 27, 1930 1,786,150 Cutler Dec. 23, 1930 1,830,178 Sperr, Jr Nov. 3, 1931 1,924,813 Sperr, Jr. Aug. 29, 1933 2,046,895 Dalamere July 7, 1936 2,141,829 Schneible Dec. 27, 1938 FOREIGN PATENTS 23,164 Great Britain Oct. 26, 1903 551,359 Germany May 14, 1931 

1. METHOD OF TREATING HOT GAS CONTAINING NAPHTHALENE COMPRISING THE STEPS OF COOLING THE GAS BY PASSING IT IN SERIES THROUGH A NUMBER OF COOLING WATER SHOWERS SPREAD ACROSS THE PATHWAY OF THE GAS, PASSING THE COOLED GAS IN CONTACT WITH A CIRCULATING NAPHTHALENE EXTRACTING AND DISSOLVING LIQUID WHILE CIRCULATING AND SPREADING SAID CIRCULATED EXTRACTING AND DISSOLVING LIQUID IN THE FORM OF A SHOWER ACROSS THE PATHWAY OF THE COOLED GAS, PASSING FROM SAID CIRCULATED LIQUID A PORTION OF SAID LIQUID TO THE COOLING WATER SHOWERS AND SUPLYING MAKE UP LIQUID OF THE SAME KIND TO SAID CIRCULATED LIQUID. 